The present invention relates to a cutting insert and cutting tool for turning operations. More specifically the invention relates to a turning insert for a bar peeling operation performed on solid or hollow bars formed of stainless steel or other heat resistant materials. The insert has a polygonal form including an upper chip face, an opposite bottom face and a clearance face located therebetween, whereby the intersection of the chip face and the clearance face forms a cutting edge.
Bar peeling as a metalworking operation means that a non-rotatable bar is axially displaced through a central hole of a rotary cutter head. The cutter head is provided with several tools which remove from the bar a thin layer of millscale, surface cracks, etc., that results from the hot rolling of such bars or tubes. In order to achieve the best results regarding tolerances and surface finish, two different types of inserts, i.e., roughing and finishing inserts, are usually combined in the same holder. One of the most commonly used inserts for bar peeling is a so-called trigonal insert as shown and described in U.S. Pat. No. 4,035,888. That insert is in the form of a regular polygonal body the corners of which are configured symmetrically about a corner bisector. Such inserts, however, have somewhat limited utility because they do not enable desired results to be achieved in terms of tolerances and surface finish when large feeds are involved.
In view thereof, it is a purpose of this invention to provide a new type of insert with nonsymmetrically formed cutting corner portions which will satisfy close tolerance demands and enable good surface finish to be achieved, even at very high feeds.
It is another purpose of the invention to provide an insert with an extended lifetime.
It is yet another purpose of the invention to provide an insert which can more efficiently reduce the tendency for vibrations to occur during a metal cutting operation.